The present invention relates to a chip type oscillator which is preferably applied to a source which generates a reference clock signal for a microprocessor or microcomputer, for example, and an oscillation circuit using this oscillator.
Microprocessors have been generally employed in the past as elements having a single function. In recent years, however, various functions in an apparatus such as a VTR or an air conditioner have increasingly employed microprocessors. Thus, a one chip microcomputer capable of performing a plurality of functions is awaited. To perform signal processing, a microcomputer necessarily requires a reference clock signal, which is usually generated by a crystal oscillator or a ceramic oscillator. The frequency of this clock signal substantially depends on a signal to be processed. Thus, a plurality of types of clock signals are required as the number of functions of a microcomputer is increased.
FIG. 1 shows a structure including two Colpitts oscillation circuits, which are formed by connecting two ceramic oscillators F.sub.1 and F.sub.2 having different frequency characteristics and four load capacitors C.sub.1 to C.sub.4 to a microcomputer M for obtaining two types of clock signals f.sub.1 and f.sub.2. Symbols A.sub.1 and A.sub.2 denote amplifiers which are contained in the microcomputer M for forming the Colpitts type oscillation circuits.
The aforementioned oscillator F.sub.1 or F.sub.2 may be prepared from a chip type oscillator which is disclosed in Japanese Utility Model Laying-Open Gazette No. 61-136630 (1986), for example. This oscillator is prepared by forming a vibrating electrode and a lead electrode on both front and back surfaces of a piezoelectric ceramic substrate respectively and bonding protective plates onto the front and back surfaces of the substrate for defining vibration cavities between the substrate and the plates. External electrodes are provided on, both sides of the protective plates to connect with the lead electrodes.
In order to apply such an oscillator as a generation source of a reference clock signal for a microcomputer, however, it is necessary to use a plurality of oscillators having different frequency characteristics for respective clock signals. For example, two oscillators and four load capacitors are required for generating two clock signals as shown in FIG. 1, and soldering is required in 12 portions in total. In this case, the number of such components is increased although the microcomputer is formed on one chip, and the circuit area is increased when these components are mounted on a printed board.